It is known that such materials are increasingly used in particular for making packing members for fragile objects or objects of complicated configuration and in the furniture industry (seats for interior use and theaters), automobile seats and accessories, toys, safety equipment and decoration, and the like.
When used as packing members these elements comprise a hollow cutout the contour of which has tended to become more and more complicated to intimately mate with the objects or parts to protect them and for increasingly varied uses.
In general to make such foam plastic pieces the wellknown technique of cutting a precompressed block of foam with a saw blade is used.
The general principle of such a cutting operation has been well-known for rather a long time. It comprises the compression of the block of foam between a plate and a rigid die comprised of a rigid plate with an appropriate aperture through which swells part of the mass of the block of compressed foam.
A form block is exerted against the block of foam between the latter and a pressor plate substantially corresponding in relief to the hollow cutout to be produced in the block of foam.
The part of the block of foam which protrudes beyond the cutout in the die is then cut at the level of the die with a cutting tool such as a saw blade. After relieving the pressure on the block of foam there is in the block in line with the die a hollow corresponding to the configuration of the relief portion.
By giving the form various configurations different cutouts, curves and depths may thus be produced in blocks of foam.
Different variations of the same technique have been proposed in the past with a view to overcoming certain specific problems.
Thus in order to obtain hollow cutouts of constant and accurate depth, it has been proposed to compress the block of foam between a plane presser plate and a die of suitable aperture, the part of the block of foam protruding beyond the die itself being compressed between the die and a lower presser plate which is likewise plane and parallel to the plane of the die.
It has also been proposed to displace a block of foam between two presser rolls, a die or form being interposed between one of the cylinders and the block of foam while a saw blade cuts a layer of foam of variable thickness depending on the amount of compression of the block of form when it encounters the cutting blade.
These various devices are, however, limited in their application and do not permit the obtention of hollow cutouts with sharp vertical walls connected by sharp angles, right angles or acute angles, with the bottom wall and particularly do not enable cutting hollow cutouts with protruding or projecting portions on the bottom wall, similar to high points of a seabed, of various contours.